#include<iostream>
#include<vector>
#include<queue>
#include<cstring>
#include<cmath>
#include<map>
#include<set>
#include<cstdio>
#include<algorithm>
#define debug(a) cout<<#a<<"="<<a<<endl;
using namespace std;
const int maxn=2e5+100;
typedef long long LL;
const LL mod=998244353;
inline LL read(){LL x=0,f=1;char ch=getchar();	while (!isdigit(ch)){if (ch=='-') f=-1;ch=getchar();}while (isdigit(ch)){x=x*10+ch-48;ch=getchar();}
return x*f;}
LL fac[maxn];
LL ksm(LL a,LL k){LL res=1;while(k>0){if(k&1) res=res*a%mod;k>>=1;a=a*a%mod;}return res%mod;}
LL ccc(LL m,LL n){ ///C(4,3)
    if(n>=m) return 1;
    else return (fac[m]%mod*ksm(fac[n],mod-2)%mod*ksm(fac[m-n],mod-2)%mod)%mod;
}
int main(void)
{
  cin.tie(0);std::ios::sync_with_stdio(false);
  fac[0]=1;
  for(LL i=1;i<maxn;i++) fac[i]=(fac[i-1]%mod*i%mod)%mod;
  LL n,m;cin>>n>>m;
  LL ans=(ccc(m,n-1)%mod*(n-2)%mod*ksm(2,n-3)%mod)%mod;
  cout<<ans<<"\n";
return 0;
}
